This invention relates to task or work chairs of the type typically associated with office work stations, and specifically for use in the performance of certain tasks such as keyboard entry of data into computers, typing and the like.
In the past, various attempts have been made to provide office chairs with several degrees of adjustability built into the chair to maximize comfort, minimize fatigue, and so on. For example, it is well known to utilize a pneumatic piston/cylinder arrangement to raise or lower the chair seat to the desired vertical position. In addition, it is known to provide vertical adjustability for a seat back mounted on a substantially vertical or L-shaped post. Typically, it is the case that the seat back mounting post is slidably mounted for horizontal movement toward or away from a seat mounting plate which is connected to the piston for vertical reciprocation. In this way, the spatial relationship of the chair back to the chair seat may be changed as desired. It is also a characteristic of this type of chair that the substantially vertical or L-shaped seat back post be constructed of a relatively thin and relatively narrow, e.g., 1.5 to 2.0 inches, strip of metal, such as steel, which will permit the seat back to recline or flex backwardly under pressure by the user. Alternatively, the seat back post may be pivotally mounted to the seat mounting plate for spring-biased reclining action.
In chairs of the above mentioned type, the pressure required to recline the seat back increases significantly as the seat back approaches the limit of its movement. As a result, rather than being in a relaxed orientation, the user is actually working hardest as the seat back reaches the limit of its reclining action.
Another problem frequently experienced with prior art chair designs has to do with the fact that to make seat adjustments, it is necessary to stand up, adjust the chair, and then sit down to see if the correct adjustment has been made. If it has not, then the process must be repeated.
Conventional chairs also in most cases lack the capability for adjusting the pitch of the seat with respect to the chair back.
It is the primary object of this invention to overcome the problems experienced with prior art office-type chairs by providing an office, or task, chair which facilitates mental activity, minimizes fatigue, conforms to all body types and sizes, and which incorporates simple manual controls, all but one of which can easily be reached while the user is sitting in the chair.
In accordance with a preferred embodiment of this invention, an office-type chair is provided in which:
(a) seat pitch can be adjusted within a 10.degree. range, so that, for example, the seat may be pitched downward for optimum computer keying tasks, or upward for other tasks;
(b) seat height with respect to the floor can be raised or lowered approximately 41/2 inches;
(c) seat depth, i.e., the distance between the seat and the seat back, may be adjusted up to two inches;
(d) the seat back pitch may be adjusted with respect to the seat, i.e., the back reclines up to 20.degree., for providing lumbar region support in all positions;
(e) the seat back may be raised or lowered up to 2 inches independently of the seat, to accommodate users of various size.
To carry out the various adjustments, a plurality of adjustment mechanisms are employed. Before describing these mechanisms in detail, however, it is important to understand the basic structure of the chair.
In one exemplary form of a chair, a pneumatic piston and cylinder extends between a five spoke pedestal base and a seat supporting brace. The brace is an integrally formed, combination horizontal seat support and generally vertical seat back support post, having a stylized L-shape.
It will be appreciated that actuation of the pneumatic piston will raise or lower both the seat and the seat back by reason of the unitary brace construction.
A lever is provided within reach of a user seated on the chair for actuating the piston/cylinder to effect upward or downward movement of the seat. This, of course, is advantageous in that the user is not required to adjust the seat in a trial and error-type operation.
The seat portion of the chair is slidably mounted on the support brace and pivotally movable with respect thereto so as to enable both horizontal sliding and pitch adjustment of the seat relative to the seat back.
A pair of concentrically arranged, inner and outer handwheels are located centrally and just behind the lower front edge of the seat for adjusting both the depth and the pitch of the seat. While the adjusting wheels are concentrically arranged, the adjustments themselves are independent of each other so that the seat is forwardly and rearwardly slidable at any adjusted pitch angle. Here again, the adjustment mechanism is within easy reach of a user seated on the chair.
The pitch adjustment is particularly useful because it allows the seat to be tilted, or canted, forwardly to a position which has been determined to be most desirable for carrying out certain office tasks, particularly keying data into a computer.
Pitch adjustment is effected by an adjustable screw, connected to the inner handwheel, which abuts a recessed dimple in a plate secured to the seat bottom. The rearward position of the seat is pivotally secured so that, upon rotation of the inner handwheel, the front of the seat is caused to pivot upwardly or downwardly, depending on the direction of rotation of the screw.
The outer handwheel of the concentric pair of handwheels acts to loosen or tighten the seat against the stationary brace to which it is slidably mounted.
A third handwheel is located on the rearward side of the seat back for purposes of adjusting the height of the seat back along the substantially vertical seat back support portion of the brace.
It is also a characteristic of the chair that the seat back and seat back support portion of the brace be reclinable with respect to the seat and seat support portion of the brace. This is accomplished as the result of carefully orchestrated removal of material from the brace in an area which connects the seat support portion to the seat back support portion. In a preferred embodiment, this connecting area is defined by a rearwardly looped, generally C-shaped integral hinge or flex connection. Material is removed from this area, preferably in the form of slots which extend throughout the C-shaped portion and, at least to some extent, into the vertical and horizontal portions of the brace. This structure permits the seat back to recline away from the seat within a range of 20.degree. from its normal, generally vertical position. In addition, because of the careful tuning of the brace through this selective removal of material, the force required to move the seat back through the first 5.degree. of its range of inclination remains generally constant. In other words, there are no increasing compressive forces exerted against the user as the seat back moves through the first 5.degree. of its 20.degree. range. It is this first 5.degree. that is considered the normal operating range most often encountered during use of the chair. Reclining between 5.degree. and 20.degree. generally occurs only sporadically while stretching, etc.
The pneumatic piston and cylinder arrangement and the five spoke pedestal base, which typically includes associated casters, are of conventional design.